The field of this invention relates to power amplifiers and more particularly to a microwave power amplifier.
Television signals are transmitted in a straight line. In order to avoid the problem of dealing with the curvature of the earth in transmitting of one television signal from one city to another city, communication satellites are used. These satellites occupy geosynchronous orbits relative to the earth.
A television program's trip to the satellite starts by means of an uplink signal. This uplink signal is defined as a carrier with this carrier including a band of frequencies clustered around six gigaHertz. This microwave frequency is chosen for one reason that it can be focused into a narrow beam by dish antennas of practical size. Also, if it is of sufficient power, this frequency penetrates quite well through moisture and dust in the upper atmosphere. The uplink signal is supplied to a dish antenna which functions to send out the signal into the narrow beam to be picked up by the satellite.
Generally, the signal that is being transmitted to the antenna is not of sufficient power to make the journey through the atmosphere to the satellite. It has been found in the prior art that to merely take the input signal and amplify it to the desired level for transmission to the satellite causes substantial distortion of the signal. The only satisfactory way that has been discovered to date to achieve the desired signal amplification is to first divide the signal into a plurality of substantially equal segments, amplify each individual segment, recombine the amplified segments into an output signal which is then transmitted to the antenna to be transmitted to the satellite.
In the past, such power amplifiers have experienced a significant coupling loss. Also, there has in the past been a substantially amount of phase error. Any maintenance of the amplifier requires shut-down of the entire system. It is common for such a power amplifier to have a tendency to overheat thereby increasing the possibility of maintenance. In the recombining of the signal within prior art amplifier, the overall combining efficiency deteriorates with frequency.